Vulkan: Restore color attachment mask-related blend states When we end up resetting blend state such as when changing to a depth-only FBO and back, we can end up adding attachment states. They need to be updated with the current GL blend state. Bug: b/210543392 Bug: angleproject:6828 Change-Id: I3419acb8081eb7d662576a75382bb8684cc0d29f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3346320 Reviewed-by: Cody Northrop <cnorthrop@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Lingfeng Yang <lfy@google.com>